Bevel-square and protractor



(No Mode-1.)

T. I'. GILCREST. BBVBL SQUARE AND PRoTRAGToR.

No. 591,964. y Patented Oct. 19, 1897.

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UNITED STATES f PATENT OFFICE.

THOMAS F. GILCREST, Oh"Y OSKALOOSA, IOWA.

BEVEL-SQUARE AND PROTRACTOR.

SPECIFICATION forming part of Letters Patent No. 591,964, dated October 19, 18'97.

Application tiled March 1 8,1 8 9 '7.

To @ZZ whom t may concern:

Be it known that 1, THOMAS F. GILCEEsr, a citizen of the United States, residing at Oskaloosa, in the county of Mahaska and State of Iowa, have invented a new and useful Bevel-Square and Protractor, of which the following is a specication.

My invention relates to bevel-squares par! ticularly adapted for use by carpenters and builders in laying o timbers for roofing and similar purposes, and designed to facilitate the marking of terminal bevels on rafters of the various kinds employed in construction, and thereby avoid ythe use of trysquare and other forms of bevel-squares heretofore in use, which necessitate the 'calculation of an# gles and distances in order to determine the proper bevels. Y

Further objects and advantages of this invention will appear in the following descrip-A tion, and the novel features thereof will be particularly pointed out in the appended claims.

In the drawings, Figure 1 is a perspective view of an instrument constructed in accordance with my invention. Fig. 2 is a detail vertical section of the joint between the ad,- j ustablc arm or tongue and the segment-plate.

Similar letters of reference indicate correspending parts in both the iigures of the drawings.

A designates'a segmental, preferably semicircular, plate having a peripheral angle-scale or protractor B.

The surface of the plate is provided with a series of concentric lines intersected by radial lines arranged at angles of forty-five degrees with each other, thus forming a series of sec-V tors bounded laterally by the radial lines, and the concentric lines between contiguous radial lines are divided to form a series of spaces which vary in length, measured along the concentric lines, according to the distances of the concentric lines, respectively, from the center of the plate, or from the common center from which the concentric lines are struck. For conveniencev in usingthe instrument the concentric lines are numbered, respectively,v from 2 to 12, beginning with the innermost and progressing outwardly, and representing the inches on the blade of a carpenters steel square, and the subdivisions of the Serial No. 628,188. (No model.)

concentric lines, each of which terminates at one' of the radial lines, are numbered consecutively, beginning with 1 at thel divisionpoints contiguous, respectively, to the relatively horizontal and vertical radial lines and progressing toward each other, and hence to-V ward the intermediate forty-flve-degree radial line. The number of subdivisions of each lsegmental line CA is equal to the number of that'line, as indicated in the columns l), before described as containing numerals ranging from 2 to 12, and representing the inches of a carpenters square. For instance, the outermost segmental line, which is formed by the portion of the outermost of the concentric lines between the horizontal numbercolumn D and the contiguous fort-yffive-degree radial line, is subdivided to form twelve spaces, and the division-marks are numbered progressively from 1 upward. In the same way the segmental line numbered ll'in the column D is divided between-the horizontal line and the adjacent Vforty-five-degree line into eleven spaces numbered progressively from 1 upward. The terminal graduation of each segmental line would obviously forty-ve-degree cut'at each end thereof is yWellknown, l have deemed it unnecessary andeven undesirable', in the interest of clearness,'to place these terminal numerals of the' segmental lines upon the instrument.

From the 4above description it will be seen that the graduations on the concentric lines are numbered progressively inward from relatively perpendicular radial lines toward the intermediate forty-five-degree radial line, thus forming two groups of graduations which are used relatively in laying oft rough timbers, the 'one to give the bevel cut at the upper end of the rafter and the 'otherto give the bevelcut at the lower end of the same rafter; and hence, for convenience in further description, I will refer to thesesections or portions of the inscribed surface of the plate, respectively, as blade and tongue groups, the former taking its name from the factthat it contains the equivalents of those measurements or graduations usually found upon the blade of a carpenters square, and the latter taking its name from the fact that it contains the equivalents of those measurements or graduations usually found upon the tongue of a carpenters square, the former group relating to the lower and the latter to the upper end of a timber. l

Attached to the diametrical lower edge of the plate, forming the body portion of the instrument embodying my invention, is a strengthening-bar or straight-edge E, to the extremities of which are attached the contiguous extremities of a clamping-bar F, the connection between the extremities of said bars consisting, in the construction illustrated, of yokes G. The clamping-bar is spaced from the front surface of the plate a sufficient distance to receive an adjustable arm or tongue H, which is pivoted by means of a clamping-screw J. This adjustable arm or tongue projects over the face of the plate which it is designed to traverse a sufficient distance to reach the peripheral degree-scale or protractor, and also projects in the opposite direction, or beyond the straight-edge, a sufficient distance to form a blade K to serve as a marking-rule to indicate the line upon which a timber is to be cut when the desired adjustment of the arm or tongue has been attained.

The use of the instrument as above described may be explained as follows: If it is desired to lay o the terminal bevels of a timber designed to occupy a position in which the run or horizont-al measurement and the rise or altitude are to each other in the ratio of twelve inches to seven inches,it is unnecessary to calculate the angle and reduce it to aprotractor, or otherwise resort to a calculation in order to ascertain the angle with a horizontal plane which said timber will occupy. The arm or tongue is simply turned until it agrees with the graduation 7 of the segmental line l2 in the blade group. This gives the lower or horizontal cut, which may be immediately transferred to the timber by placing the straight-edge of the instrument in contact with one side edge of the timber and marking the latter transversely upon the line indicated by the edge of the blade K. In the same way the graduation 7 in the segmental line l2 of the tongue group is used in the adj ustment of the arm or tongue to arrange the blade K in a position to indicate the upper or plumb cut of the timber. In the same way a timber adapted to be arranged at an inclination of which the run and riseare in any known ratio may be referred to the instrument and the arm or tongue adjusted to give the desired angles for the plumb and horizontal cuts without calculation upon the part of the operator. Obviously, when the run and rise are equal the cuts will be at an angle of fo rty-five degrees, which is given by the fortyfive-degree radial line arranged between the relatively perpendicular lines which bound ing from 13 to 24, said concentric lines being numbered, respectively, from 13 tov 24, beginning with the innermost line, and the segmental portions of those concentric lines found between contiguous forty-fivedegree lines being divided, as hereinbefore described in connection with the left-hand portion of the plate, to agree with the columnnumbers. In other words, the segmental line between either of the perpendicularly-dis-- posed radial lines and the intermediate fortyfive-degree line is divided to form twentyfour subdivisions. The concentric line numbered 19 is subdivided to form nineteen parts or spaces, and so on throughout the series. I have found in practice that these graduations give all the necessary angles used in carpentry, although it is obvious that the same principle maybe followed to secure finer graduations, and thus provide for any desired degree of accuracy which may be required by the class of work in connection with which the instrument is to be used.

It will be seen that when the tongue or arm is folded, or arranged in a position approximately parallel with the clamping-bar, its operative edges are protected by the clampingbar, to guard the same against injury when the instrument is not in use.

Various changes in the form,proportion,and the minor details of construction may be resorted to without departing from the spirit or sacrificing any of the advantages of this invention.

Having described my invention, what I claim is- 1. An instrument of the class described comprising a segmental disk and an adjustable arm or tongue to traverse the same, the surface of the plate being provided with radial lines arranged at angles of forty-five degrees to form intermediate sector shaped spaces in which are arranged series of concentric lines numbered consecutively from the innermost outward to represent horizontal runs of roof-timbers, each segmental line, between contiguous radial lines, being subdivided to form a number of spaces corresponding with the number of that line, and numbered consecutively from perpendicularly-disposed radial lines inward toward the intermediate forty-iive-degree line, to represent the rises of timbers, substantially as specified.

2. An instrument of the class described IOO IIO

having a semieiroular plate provided with graduations, and having a peripheral degreescale or protraotor, a transverse bar secured to the diametrieal edge of said plate and adapted to form a straight-edge, a clampingbar spaced from the plane of the surface of the plate and connected to said transverse bar by yokes, an adjustable arm or tongue interposed between the Clamping-bar and the surface of the plate and adapted to traverse` the latter, and a clamping-screw for connecting the clamping-bar to the plate and forining the pivot of said arm or tongue, substantially as specified.

In testimony that I elairn the foregoing as my own I have hereto attixed my signature in the presence of two Witnesses.

THOMAS F. GILCREST.

Witnesses:

J. E. DAVIS, w JNO. M. RUSSELL. 

